How to remove all shadows, lights and gloss from render? 2.8
Since you don't add any light to your scene, the render will be dark which only light up by environment light. (It will be weird when you can see object in a place with no light at all)

If you are not going to render it, use DevLook will be a better and easier way to look the scene with the power of EEVEE. You can also use viewport render if you want to get a screenshot.

And the little sphere is preview light setting overlay:



left one: reflection map
right one: diffuse map


If you want a shadowless and reflection less render:

Try to light up your scene by environment light


And also set the shader node if you want no specular at all: